Devices for methodologies for handling wafers

ABSTRACT

Disclosed are systems, devices and methodologies for handling wafers in wafer processing operations such as solvent and plasma cleaning. In an example situation, a wafer that has been separated from a support plate can be cleaned. The wafer still needs to be handled carefully during such a cleaning operation. Various devices and methodologies that facilitate efficient handling of wafers and wafer-cleaning operations are disclosed.

BACKGROUND

1. Field

The present disclosure generally relates to the field of semiconductorwafer processing technology, and more particularly, to systems andmethods for debonding a wafer from a carrier plate.

2. Description of the Related Art

In certain wafer processing operations, a wafer can be mounted to aplate for support and to facilitate handling of wafer. Such a mountingprocess is sometimes referred to as a bonding process, and can beachieved by, for example, using an adhesive.

Once the plate is no longer needed, the wafer and the plate can beseparated in a process sometimes referred to as a debonding process. Tofacilitate such a process, the bonded assembly of the wafer and platecan be heated to soften the adhesive for easier separation.

SUMMARY

In accordance with several implementations, the present disclosurerelates to an apparatus for separating a wafer from a plate. Theapparatus includes a base having a first surface and a second surfaceoffset from the first surface so as to define a first recess having aside wall with a height. The first recess has a lateral dimension thatis sufficiently large to accommodate a wafer joined to a plate as anassembly. The side wall's height can be less than or equal to thewafer's thickness. The base can further include at least one guidingfeature. The apparatus further includes a paddle dimensioned to beguided by the at least one guiding feature, such that when the assemblyis positioned on the base with the wafer received by the recess, thepaddle is capable of engaging an edge of the plate to provide a shearforce to the plate as the paddle is pushed in a lateral direction andguided by the at least one guiding feature.

In accordance with some embodiments, the paddle can define a recess onits side facing the assembly, with the recess having a lateral dimensionthat is sufficiently large to accommodate the plate. The recess can havea sidewall that dimensioned to engage the edge of the plate and providethe shear force to the plate. The lateral dimension of the recess on thepaddle can be larger than the lateral dimension of the first recess onthe base so as to allow the recess on the paddle to receive an oversizedplate. The paddle can define an aperture so as to allow viewing of theplate positioned in the recess of the paddle.

In a number of embodiments, the at least one guiding feature can includeguiding slots formed on two opposing sides of the base. The slots can bedimensioned to receive two opposing edges of the paddle. The guidingslots can be further dimensioned to allow lateral motion of the paddlein a direction that is substantially parallel to the first surface.

In certain embodiments, the second surface of the first recess on thebase can define a deeper recess dimensioned to facilitate handling ofthe wafer positioned in the first recess.

According to some embodiments, the first surface of the base can furtherdefine a second recess that is laterally distanced from the first recessand having a lateral dimension that is sufficiently large to accommodatethe plate that has been separated from the wafer by the application ofthe shear force applied to the plate. The lateral dimension of thesecond recess can be larger than the lateral dimension of the firstrecess so as to allow the second recess to receive an oversized plate.

In certain embodiments, the paddle can further include a handleconfigured to allow application of the shear force by an operator. Thehandle can be disposed on the paddle such that the shear force appliedby the operator is at a lateral position that is behind a lateralposition where the paddle engages the edge of the plate. The handle canbe disposed on the paddle such that the shear force applied by theoperator is at a lateral position that is ahead of a lateral positionwhere the paddle engages the edge of the plate.

In a number of embodiments, the second surface of the first recess candefine one or more vacuum forming features dimensioned to allow suctionholding of the plate upon application of vacuum through the one or morevacuum forming features. The one or more vacuum forming features caninclude a plurality of grooves in communication with one or more suctionforming holes.

In a number of implementations, the present disclosure relates to amethod for separating a wafer from a plate. The method includespositioning an assembly of a wafer and a plate on a surface so that thewafer engages the surface and is inhibited from sliding along thesurface. The method further includes applying a shear force on an edgeof the plate so as to yield a sliding motion of the plate relative tothe wafer, with the wafer inhibited from sliding along the surface sothat the plate separates from the wafer by its sliding motion.

In certain implementations, the method can further include applying heatto the assembly positioned on the surface. In certain embodiments, themethod can further include applying suction to the surface so as tofurther inhibit the wafer from sliding along the surface.

According to some implementations, the present disclosure relates to anapparatus having a means for holding an assembly of a wafer bonded to aplate, and a means for separating the wafer from the plate by applying aforce to and moving one of the wafer and the plate while the other ofthe wafer and the plate is inhibited from moving due to the force.

In some embodiments, the force can be applied in a direction having acomponent that is parallel to a plane defined by the assembly. The forcecan be applied to the plate and the wafer can be inhibited from movingdue to the force.

In certain implementations, the present disclosure relates to adebonding chuck for holding an assembly of a wafer and a plate bondedtogether, where the plate has a lateral dimension that is larger than alateral dimension of the wafer such that the assembly includes aperipheral area on the plate that is not covered by the wafer. The chuckincludes a first surface that defines a recess having a lateraldimension that is sufficiently large to accommodate the lateraldimension of the wafer, but less than the lateral dimension of theplate. When the assembly with the wafer facing the recess is positionedon the chuck for debonding, at least a portion of the peripheral area ofthe plate engages at least a portion of the first surface to remainoutside of the recess while the wafer is substantially within therecess. The chuck further includes a second surface disposed in therecess and separated from the first surface so as to define a depth ofthe recess. The second surface defines at least one suction openingconfigured to facilitate delivery of a suction force to the wafer viathe recess. The depth is selected to be greater than the wafer'sthickness such that when the wafer is debonded from the plate by thesuction force, the wafer is allowed to become separated from the plateand engage the second surface while the plate remains engaged to thefirst surface.

In some embodiments, the recess can have a cylindrical shape having thelateral dimension as its diameter and the depth as its height.

According to a number of embodiments, the depth of the recess can befurther selected to limit the amount of flex experienced by the wafer asit becomes separated from the plate. In certain embodiments, the depthof the recess can be selected to have a value that is greater than thewafer's thickness and less than about twice the wafer's thickness. Incertain embodiments, the depth of the recess can be selected to have avalue that is greater than the wafer's thickness by an amount in a rangeof about 0.001″ to 0.002″.

In a number of embodiments, the at least one suction opening on thesecond surface can include one or more grooves configured to be incommunication with an external vacuum source. The one or more groovescan be distributed on the second surface so as to distribute the suctionforce provided to the wafer. The one or more grooves can include aplurality of grooves shaped in concentric circles about a center of thesecond surface. The one or more grooves can include at least one groovethat extends radially from a center of the second surface. The one ormore grooves can be configured such that the distributed suction forceresults in the separation of the wafer from the plate begins at thewafer's periphery.

In accordance with a number of embodiments, the first and secondsurfaces can be joined by a side wall. In certain embodiments, the firstsecond surfaces can be substantially parallel. In certain embodiments,the side wall can be substantially perpendicular to both of the firstand second surfaces.

In certain embodiments, the side wall can define at least one openingdimensioned to limit a pressure difference between the recess andoutside of the recess during the application of the suction force.

According to some embodiments, the second surface can further define atleast one relief opening in communication with at least a portion of thesuction opening and outside of the recess so as to limit a pressuredifference between the recess and the at least one suction opening whenthe wafer engages the second surface and experiencing the suction force.

In some embodiments, at least a portion of the second surface can beconfigured to be in thermal contact with a heat source so as to allowheating of the assembly positioned on the chuck.

In a number of implementations, the present disclosure relates to awafer debonding system having the debonding chuck summarized above.

In some embodiments, the system can include a manual debonding systemconfigured so that the positioning of the assembly on the chuck isperformed manually by an operator. In certain embodiments, the systemcan further include a control component configured to facilitate anautomated sequence of debonding operations. The sequence of debondingoperations can include positioning of the assembly on the chuck andremoval of the separated wafer and the plate from the chuck.

In certain embodiments, the system can further include a roboticcomponent configured to perform the sequence of debonding operations. Incertain embodiments, the system can further include a lift mechanismcapable of being in extended and retracted orientations. The liftmechanism in its extended orientation can be configured to receive theassembly from the robotic component at a location spaced from the firstsurface. The lift mechanism in its retracted orientation can beconfigured to position the assembly on the chuck. In certainembodiments, the lift mechanism can include a plurality of lift pinsdisposed along the first surface so as to allow the pins' movementsbetween the extended and retracted orientations without directlytouching the wafer. In certain embodiments, each of the plurality oflift pins is configured to be capable of being controlled independently.

In some embodiments, the system can further include a cleaning componentconfigured to be capable of cleaning the separated wafer.

In a number of implementations, the present disclosure relates to amethod for debonding a wafer from an oversized plate. The methodincludes positioning an assembly of a wafer and a plate on a vacuumchuck that is dimensioned to support the assembly by an oversizedportion of the plate such that the wafer faces the vacuum chuck. Themethod further includes applying a suction to the vacuum chuck so as toyield a suction force being applied to the wafer. The plate is inhibitedfrom following the wafer due to the vacuum chuck supporting theoversized portion of the plate so that the wafer is pulled away from theplate by the suction force. The method further includes receiving theseparated wafer in a recess defined by the vacuum chuck.

In some embodiments, the method can further include removing the platefrom its supported position on the vacuum chuck. In certain embodiments,the method can further include removing the wafer from the recess.

In a number of embodiments, the method can further include applying heatto the assembly positioned on the chuck.

According to some embodiments, the applying of the suction to the vacuumchuck can include applying a distributed suction force to the wafer. Thedistributed suction force applied to the wafer can result in the waferbeing separated from the oversized plate starting from the wafer's edge.

In certain implementations, the present disclosure relates to adebonding apparatus for separating a wafer from a plate. The plate has alateral dimension that is larger than a lateral dimension of the wafersuch that an assembly of the wafer and the plate includes a peripheralarea on the plate that is not covered by the wafer. The apparatusincludes a chuck having a vacuum surface configured to receive the waferof the assembly. The apparatus further includes one or more separationmembers disposed relative to the vacuum surface so as to allow the oneor more separation members to engage at least a portion of the plate andmove the at least a portion of the plate without directly touching thewafer so as to allow separation of the plate away from the wafer bymoving the one or more separation members when the wafer is held on thevacuum surface by application of vacuum.

In a number of embodiments, the one or more separation members caninclude one or more lift members. The one or more lift members caninclude a plurality of lift pins dimensioned and disposed so as toengage the peripheral area on the plate but not the wafer. At least oneof the plurality of lift pins can be configured to be capable of movingindependently from other lift pins.

According to some embodiments, the one or more lift members can includea blade dimensioned and disposed so as to engage the peripheral area onthe plate but not the wafer.

In some embodiments, the one or more separation members can include asuction member disposed on the side of the plate that is opposite fromthe side engaging the wafer. The suction member can be disposed awayfrom the plate's center so as to allow one side of the plate to beseparated first from the wafer.

In certain embodiments, the vacuum surface can be defined by a floorsurface of a recess having a lateral dimension that is larger than thelateral dimension of the wafer, but less than the lateral dimension ofthe plate. In certain embodiments, the recess can have a depth that canbe selected to be greater than the wafer's thickness such that uponapplication of the vacuum, the wafer can be pulled away from the plateby the suction force and allowed to become separated from the plate andengage the vacuum surface of the recess.

In a number of implementations, the present disclosure relates to anautomated debonding system having the debonding apparatus summarizedabove.

In a number of implementations, the present disclosure relates to anapparatus having a means for holding an assembly of a wafer bonded to aplate, and a means for separating the wafer from the plate by applying aforce to and moving one of the wafer and the plate while the other ofthe wafer and the plate is inhibited from moving due to the force.

In some implementations, the present disclosure relates to a system fordebonding a wafer bonded to a plate. The plate has a lateral dimensionthat is larger than a lateral dimension of the wafer such that thebonded wafer and plate assembly includes a peripheral area on the platethat is not covered by the wafer. The system includes a base having afirst surface and a second surface offset from the first surface so asto define a recess having a side wall with a height. The recess has alateral dimension that is sufficiently large to accommodate the lateraldimension of the wafer, but less than the lateral dimension of theplate, such that when the assembly with the wafer facing the recess ispositioned on the base for debonding, at least a portion of the wafer iswithin the recess while the plate remains outside of the recess. Thesystem further includes a force applicator configured provide aseparating force to at least one of the wafer and the plate. The heightof the side wall is selected so that upon application of the separatingforce, one of the wafer and the plate is inhibited from moving in adirection along the separating force while the other one moves in thedirection of the separating force.

In some embodiments, the base and the force applicator can be configuredso as to allow the force applicator to slide along a direction that issubstantially parallel to a plane defined by the assembly, such that theseparating force provides a shear force between the plate and the wafer.In certain embodiments, the side wall of the recess can be configured toengage a leading edge of the wafer and the force applicator can beconfigured to engage a lagging edge of the plate so that uponapplication of the shear force, the plate can be allowed to slide alongthe direction while the engagement of the leading edge of the wafer withthe side wall can inhibit the movement of the wafer along the direction.

In a number of embodiments, the base can be configured so that theheight of the side wall can be greater than the thickness of the wafer.The second surface can have one or more suction features. The forceapplicator can be in communication with the suction features andconfigured to provide suction to the recess via the suction features,such that the separating force can provide a pulling force on the waferalong a direction having a component perpendicular to the assembly. Incertain embodiments, at least a portion of the first surface can beconfigured to engage at least a portion of the peripheral area on theplate so that upon application of the pulling force, the wafer can beallowed to be pulled away from the plate while the plate's engagementwith the first surface can inhibit the movement of the plate along thedirection.

According to certain implementations, the present disclosure relates toa wafer holding device. The device includes a plate having a surfacedimensioned to receive a wafer thereon. The device further includes aplurality of features formed on the surface and distributed along thesurface so that the wafer positioned on the surface is in contact withat least some of the features and offset from the surface.

In a number of embodiments, the device can further include one or morewafer-retaining features formed along an edge of the plate. Theretaining features can be configured so that when the plate is orientedwith the edge downward and the surface facing upward and at an angleaway from horizontal, the wafer held thereon can engage the retainingfeatures and can be inhibited from falling off the plate. The one ormore wafer-retaining features can include two J-shaped hook features onthe side of the first surface. The two hook features can be by an openspace dimensioned to allow drainage of the liquid.

In certain embodiments, the plurality of features can include aplurality of bumps. Each of the plurality of bumps can include a curvessurface dimensioned to engage the wafer.

In some embodiments, the features can be dimensioned and distributed toallow efficient movement of liquid relative to the wafer during cleaningand drying operations.

In some embodiments, the edge having the retaining features can have acurved shape to conform to the curved edge of the wafer.

In a number of embodiments, the plate can define a handling tab on anedge opposite from the edge having the retaining features.

According to some implementations, the present disclosure relates to acassette for holding one or more of the wafer holding device assummarized above. The cassette can be configured to be capable of beingin collection orientation and a cleaning orientation, The cassette canbe further configured so that when in the collection orientation, thewafer holding device can be held in the cassette approximatelyhorizontally, and when in the cleaning orientation, the wafer holdingdevice can be held at an angle away from the vertical so that the waferis retained on the plate.

According to some embodiments, the angle can be in a range of about 1degree to 60 degrees relative to the vertical, about 10 degrees to 45relative to the vertical, or about 20 degrees to 35 relative to thevertical.

According to some implementations, the present disclosure relates to acassette for holding one or more of the wafer holding device assummarized above. The cassette can be configured so the wafer holdingdevice can be held in the cassette approximately horizontally to allowplasma cleaning of a wafer held on the wafer holding device.

According to some embodiments, the cassette can further include a topcover disposed above a location where the uppermost wafer holding deviceis held. The top cover can be dimensioned to provide a cover for a waferon the uppermost wafer holding device to provide the wafer with asimilar plasma cleaning environment as other wafers held underneath.

In some implementations, the present disclosure relates to a method forcleaning a wafer. The method includes placing a wafer to be cleaned on awafer-holder. The method further includes positioning the wafer-holderwith the wafer thereon so that the wafer-holder is held at an angle awayfrom the vertical. The method further includes applying a cleaningsolution to the wafer held at the angle. The method further includesdraining the cleaning solution from the wafer, with the wafer being heldat the angle facilitating the draining.

In some implementations, the present disclosure relates to a method forplasma cleaning a wafer. The method includes placing a wafer to beplasma cleaned on a wafer-holder. The method further includespositioning a plurality of the wafer-holders with wafers thereon so thatthe wafers are held in a spaced stack. The method further includesproviding a cover above the uppermost one of the wafers. The methodfurther includes applying a cleaning plasma to the wafers. The coverprovides an exposure to the cleaning plasma to the uppermost wafer thatis similar to the wafers underneath the uppermost wafer.

In certain implementations, the present disclosure relates to anoptically transparent disk for bonding a semiconductor wafer thereto toprovide support for the wafer. The disk can have a diameter and formedfrom a chemical resistant material. The diameter of the disk can belarger than the wafer's diameter by approximately 3% or more, byapproximately 5% or more, by approximately 6% or more, or byapproximately 10% or more. In certain embodiments, the material caninclude sapphire or borosilicate.

For purposes of summarizing the disclosure, certain aspects, advantagesand novel features of the inventions have been described herein. It isto be understood that not necessarily all such advantages may beachieved in accordance with any particular embodiment of the invention.Thus, the invention may be embodied or carried out in a manner thatachieves or optimizes one advantage or group of advantages as taughtherein without necessarily achieving other advantages as may be taughtor suggested herein.

The present disclosure relates to U.S. patent application Ser. No.______ [Attorney Docket SKYWRKS.095A], titled “FIXTURES AND METHODS FORUNBONDING WAFERS BY SHEAR FORCE,” and U.S. patent application Ser. No.______ [Attorney Docket SKYWRKS.108A], titled “DEBONDER AND RELATEDDEVICES AND METHODS FOR SEMICONDUCTOR FABRICATION,” each filed on evendate herewith and each hereby incorporated by reference herein in itsentirety.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an example sequence of wafer processing for formingthrough-wafer features such as vias.

FIGS. 2A-2V show examples of structures at various stages of theprocessing sequence of FIG. 1.

FIG. 3 shows a more detailed debonding process that can be implementedas a part of the process of FIG. 1.

FIGS. 4A-4D show that in certain implementations, an assembly of a waferbonded to a carrier plate can be heated so as to weaken the bond, so asto allow mechanical separation of the wafer from the carrier plate in anumber of different ways.

FIG. 5 shows examples of apparatus configured to separate a wafer from acarrier plate by application of shear force.

FIG. 6 shows an underside of a sliding member for the first of theexample apparatus of FIG. 5.

FIG. 7 shows an underside of a sliding member for the second of theexample apparatus of FIG. 5.

FIG. 8 shows a perspective view of a debonding chuck configured to allowseparation of a wafer from a carrier plate by application of vacuum.

FIGS. 9A and 9B show side sectional and plan views of the debondingchuck of FIG. 8.

FIGS. 10A-10E show an example sequence of the wafer being separated fromthe carrier plate by the debonding chuck of FIG. 8.

FIGS. 11A-11C show that in certain implementations, a system having avacuum-based debonding apparatus can be configured to include a sensorcomponent and/or a vacuum control component so as to facilitate certaindebonding operations such as application and termination of vacuum.

FIGS. 12A and 12B show that in certain embodiments, a debonding chuckcan be configured so that at least some portion of its recess and/orsuction distributing grooves can be in communication with the outside soas to limit pressure differentials.

FIG. 13A shows that in certain embodiments, the debonding chuck of FIG.8 can be implemented in a manual debonding system that can include aheater (on which a wafer-carrier assembly is being heated) and adebonding apparatus.

FIG. 13B shows the heated wafer-carrier assembly on the debondingapparatus for mechanical separation.

FIGS. 14A and 14B show that in certain implementations, a wafer holdercan be provided for holding a separated wafer (e.g., from the manualdebonding system of FIGS. 13A and 13B) to facilitate one or morepost-separation operations such as cleaning.

FIG. 14C shows the wafer holder of FIG. 14A holding a wafer.

FIG. 15A shows that in certain implementations, a first cassette devicecan be configured to hold a number of the wafer holders of FIGS. 14A and14B, such that in its first orientation, the cassette device facilitatescollection of separated wafers from the manual debonding system of FIGS.13A and 13B.

FIG. 15B shows the cassette device of FIG. 15A in its second orientationthat facilitates cleaning and drying of the wafers.

FIG. 16 shows that in certain implementations, a second cassette devicecan be configured to hold a number of the wafer holders of FIGS. 14A and14B so as to facilitate operations such as a plasma ash process toremove residues from the cleaned wafers.

FIG. 17 shows that in certain embodiments, the debonding chuck of FIG. 8can be implemented in an automated debonding system.

FIG. 18A shows the debonding chuck implemented in the example automatedsystem of FIG. 17.

FIG. 18B shows that in certain embodiments, the automated system caninclude one or more devices for handling the wafer-carrier assembly andthe separated wafer and carrier.

FIG. 19 shows a cleaning station that is part of the example automatedsystem of FIG. 17.

FIG. 20 shows that in certain implementations, one or more collectiondevices can be provided to collect separated wafers and carriers fromthe automated system of FIG. 17.

DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS

The headings provided herein, if any, are for convenience only and donot necessarily affect the scope or meaning of the claimed invention.

Provided herein are various methodologies and devices for processingwafers such as semiconductor wafers. FIG. 1 shows an example of aprocess 10 where a functional wafer is further processed to formthrough-wafer features such as vias and back-side metal layers. Asfurther shown in FIG. 1, the example process 10 can include bonding of awafer to a carrier for support and/or to facilitate handling during thevarious steps of the process, and debonding of the wafer from thecarrier upon completion of such steps. FIG. 1 further shows that such awafer separated from the carrier can be further processed so as to yielda number of dies.

In the description herein, various examples are described in the contextof GaAs substrate wafers. It will be understood, however, that some orall of the features of the present disclosure can be implemented inprocessing, of other types of semiconductor wafers. Further, some of thefeatures can also be applied to situations involving non-semiconductorwafers.

In the description herein, various examples are described in the contextof back-side processing of wafers. It will be understood, however, thatsome or all of the features of the present disclosure can be implementedin front-side processing of wafers.

In the process 10 of FIG. 1, a functional wafer can be provided (block11). FIG. 2A depicts a side view of such a wafer 30 having first andsecond sides. The first side can be a front side, and the second side aback side.

FIG. 2B depicts an enlarged view of a portion 31 of the wafer 30. Thewafer 30 can include a substrate layer 32 (e.g., a GaAs substratelayer). The wafer 30 can further include a number of features formed onor in its front side. In the example shown, a transistor 33 and a metalpad 35 are depicted as being formed the front side. The exampletransistor 33 is depicted as having an emitter 34 b, bases 34 a, 34 c,and a collector 34 d. Although not shown, the circuitry can also includeformed passive components such as inductors, capacitors, and source,gate and drain for incorporation of planar field effect transistors(FETs) with heterojunction bipolar transistors (HBTs). Such structurescan be formed by various processes performed on epitaxial layers thathave been deposited on the substrate layer.

Referring to the process 10 of FIG. 1, the functional wafer of block 11can be tested (block 12) in a number of ways prior to bonding. Such apre-bonding test can include, for example, DC and RF tests associatedwith process control parameters.

Upon such testing, the wafer can be bonded to a carrier (block 13). Incertain implementations, such a bonding can be achieved with the carrierabove the wafer. Thus, FIG. 2C shows an example assembly of the wafer 30and a carrier 40 (above the wafer) that can result from the bonding step13. In certain implementations, the wafer and carrier can be bondedusing temporary mounting adhesives such as wax or commercially availableCrystalbond™. In FIG. 2C, such an adhesive is depicted as an adhesivelayer 38.

In certain implementations, the carrier 40 can be a plate having a shape(e.g., circular) similar to the wafer it is supporting. Preferably, thecarrier plate 40 has certain physical properties. For example, thecarrier plate 40 can be relatively rigid for providing structuralsupport for the wafer. In another example, the carrier plate 40 can beresistant to a number of chemicals and environments associated withvarious wafer processes. In another example, the carrier plate 40 canhave certain desirable optical properties to facilitate a number ofprocesses (e.g., transparency to accommodate optical alignment andinspections)

Materials having some or all of the foregoing properties can includesapphire, borosilicate (also referred to as Pyrex), quartz, and glass(e.g., SCG72).

In certain implementations, the carrier plate 40 can be dimensioned tobe larger than the wafer 30. Thus, for circular wafers, a carrier platecan also have a circular shape with a diameter that is greater than thediameter of a wafer it supports. Such a larger dimension of the carrierplate can facilitate easier handling of the mounted wafer, and thus canallow more efficient processing of areas at or near the periphery of thewafer.

Tables 1A and 1B list various example ranges of dimensions and exampledimensions of some example circular-shaped carrier plates that can beutilized in the process 10 of FIG. 1.

TABLE 1A Carrier plate Carrier plate diameter range thickness rangeWafer size Approx. 100 to 120 mm Approx. 500 to 1500 um Approx. 100 mmApprox. 150 to 170 mm Approx. 500 to 1500 um Approx. 150 mm Approx. 200to 220 mm Approx. 500 to 2000 um Approx. 200 mm Approx. 300 to 320 mmApprox. 500 to 3000 um Approx. 300 mm

TABLE 1B Carrier plate diameter Carrier plate thickness Wafer sizeApprox. 110 mm Approx. 1000 um Approx. 100 mm Approx. 160 mm Approx.1300 um Approx. 150 mm Approx. 210 mm Approx. 1600 um Approx. 200 mmApprox. 310 mm Approx. 1900 um Approx. 300 mm

An enlarged portion 39 of the bonded assembly in FIG. 2C is depicted inFIG. 2D. The bonded assembly can include the GaAs substrate layer 32 onwhich are a number of devices such as the transistor (33) and metal pad(35) as described in reference to FIG. 2B. The wafer (30) having suchsubstrate (32) and devices (e.g., 33, 35) is depicted as being bonded tothe carrier plate 40 via the adhesive layer 38.

As shown in FIG. 2D, the substrate layer 32 at this stage has athickness of d1, and the carrier plate 40 has a generally fixedthickness (e.g., one of the thicknesses in Table 1). Thus, the overallthickness (T_(assembly)) of the bonded assembly can be determined by theamount of adhesive in the layer 38.

In a number of processing situations, it is preferable to providesufficient amount of adhesive to cover the tallest feature(s) so as toyield a more uniform adhesion between the wafer and the carrier plate,and also so that such a tall feature does not directly engage thecarrier plate. Thus, in the example shown in FIG. 2D, the emitterfeature (34 b in FIG. 2B) is the tallest among the example features; andthe adhesive layer 38 is sufficiently thick to cover such a feature andprovide a relatively uninterrupted adhesion between the wafer 30 and thecarrier plate 40.

Referring to the process 10 of FIG. 1, the wafer—now mounted to thecarrier plate—can be thinned so as to yield a desired substratethickness in blocks 14 and 15. In block 14, the back side of thesubstrate 32 can be ground away (e.g., via two-step grind with coarseand fine diamond-embedded grinding wheels) so as to yield anintermediate thickness-substrate (with thickness d2 as shown in FIG. 2E)with a relatively rough surface. In certain implementations, such agrinding process can be performed with the bottom surface of thesubstrate facing downward.

In block 15, the relatively rough surface can be removed so as to yielda smoother back surface for the substrate 32. In certainimplementations, such removal of the rough substrate surface can beachieved by an O2 plasma ash process, followed by a wet etch processutilizing acid or base chemistry. Such an acid or base chemistry caninclude HCl, H₂SO₄, HNO₃, H₃PO₄, H₃COOH, NH₄OH, H₂O₂, etc., mixed withH₂O₂ and/or H₂O. Such an etching process can provide relief frompossible stress on the wafer due to the rough ground surface.

In certain implementations, the foregoing plasma ash and wet etchprocesses can be performed with the back side of the substrate 32 facingupward. Accordingly, the bonded assembly in FIG. 2F depicts the wafer 30above the carrier plate 40. FIG. 2G shows the substrate layer 32 with athinned and smoothed surface, and a corresponding thickness of d3.

By way of an example, the pre-grinding thickness (d1 in FIG. 2D) of a150 mm (also referred to as “6-inch”) GaAs substrate can beapproximately 675 μm. The thickness d2 (FIG. 2E) resulting from thegrinding process can be in a range of approximately 102 μm to 120 μm.The ash and etching processes can remove approximately 2 μm to 20 μm ofthe rough surface so as to yield a thickness of approximately 100 μm.(d3 in FIG. 2G). Other thicknesses are possible.

In certain situations, a desired thickness of theback-side-surface-smoothed substrate layer can be an important designparameter. Accordingly, it is desirable to be able to monitor thethinning (block 14) and stress relief (block 15) processes. Since it canbe difficult to measure the substrate layer while the wafer is bonded tothe carrier plate and being worked on, the thickness of the bondedassembly can be measured so as to allow extrapolation of the substratelayer thickness. Such a measurement can be achieved by, for example, agas (e.g., air) back pressure measurement system that allows detectionof surfaces (e.g., back side of the substrate and the “front” surface ofthe carrier plate) without contact.

As described in reference to FIG. 2D, the thickness (T_(assembly)) ofthe bonded assembly can be measured; and the thicknesses of the carrierplate 40 and the un-thinned substrate 32 can have known values. Thus,subsequent thinning of the bonded assembly can be attributed to thethinning of the substrate 32; and the thickness of the substrate 32 canbe estimated.

Referring to the process 10 of FIG. 1, the thinned and stress-relievedwafer can undergo a through-wafer via formation process (block 16).FIGS. 2H-2J show different stages during the formation of a via 44. Sucha via is described herein as being formed from the back side of thesubstrate 32 and extending through the substrate 32 so as to end at theexample metal pad 35. It will be understood that one or more featuresdescribed herein can also be implemented for other deep features thatmay not necessarily extend all the way through the substrate. Moreover,other features (whether or not they extend through the wafer) can beformed for purposes other than providing a pathway to a metal feature onthe front side.

To form an etch resist layer 42 that defines an etching opening 43 (FIG.2H), photolithography can be utilized. Coating of a resist material onthe back surface of the substrate, exposure of a mask pattern, anddeveloping of the exposed resist coat can be achieved in known manners.In the example configuration of FIG. 2H, the resist layer 42 can have athickness in a range of about 15 μm to 20 μm.

To form a through-wafer via 44 (FIG. 21) from the back surface of thesubstrate to the metal pad 35, techniques such as dry inductivelycoupled plasma (ICP) etching (with chemistry such as BCl₃/Cl₂) can beutilized. In various implementations, a desired shaped via can be animportant design parameter for facilitating proper metal coveragetherein in subsequent processes.

FIG. 2J shows the formed via 44, with the resist layer 42 removed. Toremove the resist layer 42, photoresist strip solvents such as NMP(N-methyl-2-pyrrolidone) and EKC can be applied using, for example, abatch spray tool. In various implementations, proper removal of theresist material 42 from the substrate surface can be an importantconsideration for subsequent metal adhesion. To remove residue of theresist material that may remain after the solvent strip process, aplasma ash (e.g., O₂) process can be applied to the back side of thewafer.

Referring to the process 10 of FIG. 1, a metal layer can be formed onthe back surface of the substrate 32 in block 17. FIGS. 2K and 2L showexamples of adhesion/seed layers and a thicker metal layer.

FIG. 2K shows that in certain implementations, an adhesion layer 45 suchas a nickel vanadium (NiV) layer can be formed on surfaces of thesubstrate's back side and the via 44 by, for example, sputtering.Preferably, the surfaces are cleaned (e.g., with HCl) prior to theapplication of NiV. FIG. 2K also shows that a seed layer 46 such as athin gold layer can be formed on the adhesion layer 45 by, for example,sputtering. Such a seed layer facilitates formation of a thick metallayer 47 such as a thick gold layer shown in FIG. 2L. In certainimplementations, the thick gold layer can be formed by a platingtechnique.

In certain implementations, the gold plating process can be performedafter a pre-plating cleaning process (e.g., O₂ plasma ash and HClcleaning). The plating can be performed to form a gold layer of about 3μm to 6 μm to facilitate the foregoing electrical connectivity and heattransfer functionalities. The plated surface can undergo a post-platingcleaning process (e.g., O₂ plasma ash).

The metal layer formed in the foregoing manner forms a back side metalplane that is electrically connected to the metal pad 35 on the frontside. Such a connection can provide a robust electrical reference (e.g.,ground potential) for the metal pad 35. Such a connection can alsoprovide an efficient pathway for conduction of heat between the backside metal plane and the metal pad 35.

Thus, one can see that the integrity of the metal layer in the via 44and how it is connected to the metal pad 35 and the back side metalplane can be important factors for the performance of various devices onthe wafer. Accordingly, it is desirable to have the metal layerformation be implemented in an effective manner. More particularly, itis desirable to provide an effective metal layer formation in featuressuch as vias that may be less accessible.

Referring to the process 10 of FIG. 1, the wafer having a metal layerformed on its back side can undergo a street formation process (block18). FIGS. 2M-2O show different stages during the formation of a street50. Such a street is described herein as being formed from the back sideof the wafer and extending through the metal layer 52 to facilitatesubsequent singulation of dies. It will be understood that one or morefeatures described herein can also be implemented for other street-likefeatures on or near the back surface of the wafer. Moreover, otherstreet-like features can be formed for purposes other than to facilitatethe singulation process.

To form an etch resist layer 48 that defines an etching opening 49 (FIG.2M), photolithography can be utilized. Coating of a resist material onthe back surface of the substrate, exposure of a mask pattern, anddeveloping of the exposed resist coat can be achieved in known manners.

To form a street 50 (FIG. 2N) through the metal layer 52, techniquessuch as wet etching (with chemistry such as potassium iodide) can beutilized. A pre-etching cleaning process (e.g., O₂ plasma ash) can beperformed prior to the etching process. In various implementations, thethickness of the resist 48 and how such a resist is applied to the backside of the wafer can be important considerations to prevent certainundesirable effects, such as via rings and undesired etching of via rimduring the etch process.

FIG. 2O shows the formed street 50, with the resist layer 48 removed. To“remove the resist layer 48, photoresist strip solvents such as NMP(N-methyl-2-pyrrolidone) can be applied using, for example, a batchspray tool. To remove residue of the resist material that may remainafter the solvent strip process, a plasma ash (e.g., O₂) process can beapplied to the back side of the wafer.

In the example back-side wafer process described in reference to FIGS. 1and 2, the street (50) formation and removal of the resist (48) yields awafer that no longer needs to be mounted to a carrier plate. Thus,referring to the process 10 of FIG. 1, the wafer is debonded orseparated from the carrier plate in block 19. FIGS. 2P-2R show differentstages of the separation and cleaning of the wafer 30.

In certain implementations, separation of the wafer 30 from the carrierplate 40 can be performed with the wafer 30 below the carrier plate 40(FIG. 2P). To separate the wafer 30 from the carrier plate 40, theadhesive layer 38 can be heated to reduce the bonding property of theadhesive. For the example Crystalbond™ adhesive, an elevated temperatureto a range of about 130° C. to 170° C. can melt the adhesive tofacilitate an easier separation of the wafer 30 from the carrier plate40. Some form of mechanical force can be applied to the wafer 30, thecarrier plate 40, or some combination thereof, to achieve suchseparation (arrow 53 in FIG. 2P). In various implementations, achievingsuch a separation of the wafer with reduced likelihood of scratches andcracks on the wafer can be an important process parameter forfacilitating a high yield of good dies.

In FIGS. 2P and 2Q, the adhesive layer 38 is depicted as remaining withthe wafer 30 instead of the carrier plate 40. It will be understood thatsome adhesive may remain with the carrier plate 40.

FIG. 2R shows the adhesive 38 removed from the front side of the wafer30. The adhesive can be removed by a cleaning solution (e.g., acetone),and remaining residues can be further removed by, for example, a plasmaash (e.g., O₂) process.

Referring to the process 10 of FIG. 1, the debonded wafer of block 19can be tested (block 20) in a number of ways prior to singulation. Sucha post-debonding test can include, for example, resistance of the metalinterconnect formed on the through-wafer via using process controlparameters on the front side of the wafer. Other tests can addressquality control associated with various processes, such as quality ofthe through-wafer via etch, seed layer deposition, and gold plating.

Referring to the process 10 of FIG. 1, the tested wafer can be cut toyield a number of dies (block 21). In certain implementations, at leastsome of the streets (50) formed in block 18 can facilitate the cuttingprocess. FIG. 2S shows cuts 61 being made along the streets 50 so as toseparate an array of dies 60 into individual dies. Such a cuttingprocess can be achieved by, for example, a diamond scribe and rollerbreak, saw or a laser.

In the context of laser cutting, FIG. 2T shows an effect on the edges ofadjacent dies 60 cut by a laser. As the laser makes the cut 61, a roughedge feature 62 (commonly referred to as recast) typically forms.Presence of such a recast can increase the likelihood of formation of acrack therein and propagating into the functional part of thecorresponding die.

Thus, referring to the process 10 in FIG. 1, a recast etch process usingacid and/or base chemistry (e.g., similar to the examples described inreference to block 15) can be performed in block 22. Such etching of therecast feature 62 and defects formed by the recast, increases the diestrength and reduces the likelihood of die crack failures (FIG. 2U).

Referring to the process 10 of FIG. 1, the recast etched dies (FIG. 2V)can be further inspected and subsequently be packaged.

As described herein in reference to FIGS. 1 and 2, some operations inthe process 10 can benefit from having a wafer temporarily bonded to acarrier plate. Once such operations are completed, the wafer can beremoved or debonded from the carrier plate. FIGS. 3-20 show variousdevices and methodologies for such debonding of wafers.

It will be understood that one or more features associated withdebonding devices and methodologies can be implemented in the examplethrough-wafer via process described in reference to FIGS. 1 and 2, aswell as in other processing situations. It will also be understood thatone or more features associated with debonding devices and methodologiescan be implemented in different types of semiconductor-based wafers,including but not limited to those formed from semiconductor materialssuch as groups IV, III-V, II-VI, I-VII, IV-VI, V-VI, II-V; oxides;layered semiconductors; magnetic semiconductors; organic semiconductors;charge-transfer complexes; and other semiconductors. Further, some ofthe features described herein can also be implemented in situationsinvolving separation of non-semiconductor-based wafers from anotherstructure.

FIG. 3 depicts a debonding process where a bonded assembly 100 (a wafer30 and a carrier plate 40 bonded by an adhesive layer 38) is provided toa debonding system 110. The debonding system 110 is depicted asseparating the wafer 30 and the carrier plate 40. The adhesive layer 38may remain on the wafer 30, on the carrier plate 40, or some combinationthereof.

In certain implementations, the separated wafer 30 can be subjected to acleaning system 120 so as to yield a cleaned wafer 30. In certainimplementations, the carrier plate 40 can also be cleaned for re-use.

FIG. 4A shows that in certain implementations, a carrier plate 40 canhave a larger dimension (e.g., diameter D1) than that of a wafer 30(e.g., diameter D2). Thus, when the wafer 30 is positioned appropriatelyrelative to the carrier plate 40 (e.g., approximately centered), thecarrier plate's edge extends beyond the wafer edge by an amountindicated as AR. In certain implementations of the present disclosure,such a configuration can be utilized to facilitate an effectiveseparation of the wafer 30. More particularly, the carrier plate 40itself can provide a structure facilitating the separation of the wafer.Such a feature can be advantageous over certain debonding techniques,especially when relatively thin wafers such as GaAs wafers in varioussizes (e.g., 4-inch and 6-inch diameters) need to be separated fromcarrier plates such as sapphire plates.

For example, certain debonders can include two heated vacuum chuckassemblies—one to hold the wafer, and the other to hold the carrierplate. Upon heating of the wafer-carrier assembly, the two chucks areseparated so as to pull their respective held pieces. Thus, opposingpulling forces are applied to both the wafer and the carrier plate.

Such a design can be disadvantageous in a number of ways. For example,it can be relatively costly to design, build and operated both chuckassemblies in a reliable and coordinated manner while handling andseparating relatively fragile wafers. In another example, once the twochucks converge to form a vacuum grip on the wafer and the carrierplate, the view of the wafer-carrier assembly becomes obscured.Accordingly, it can be difficult to monitor, troubleshoot, and/oroptimize the debonding process. In yet another example, such a debondingmechanism can sometimes result in wafer-carrier assemblies not debondingor in wafers cracking.

Referring to FIG. 4A, the distance between the inner side (wafer-bondingside) of the carrier plate 40 and the outer side (away from the carrierplate) of the wafer 30 is depicted as T. In certain implementations,such a dimension can provide one or more design parameters for debondingapparatus. Additional details concerning such design parameters aredescribed herein.

FIG. 4B shows that in certain implementations, heat can be applied tothe wafer-carrier assembly so as to melt the adhesive 38, therebyyielding a more separable assembly 130 having a melted adhesive layer132. Such heat can be provided in a number of ways. For example, thewafer-carrier assembly can be positioned on a heating surface so as toreceive heat from underneath. Such a heating surface can be part of aseparate heating device, or part of a debonding chuck described herein.In another example, heat can be applied from other directions (e.g.,top) and/or by other methods (e.g., infrared lamp).

For the purpose of description, it will be understood that “melt,”“melted,” or “melting” in the context of the adhesive (38) can includesituations where the adhesive is softened sufficiently to allowrelatively easy separation of the wafer and carrier plate which werebonded by the adhesive. In some situations, such softening of theadhesive can occur at a temperature that is lower than the temperaturewhere the solid-to-liquid phase transition occurs.

Although the adhesive is melted in FIG. 4B, at least some mechanicalforce needs to be applied to separate the wafer from the carrier platedue to surface tension. FIG. 4C shows that in certain implementations,such a mechanical force can be in the form of a shear force (depicted asarrow 146) applied to at least one of the wafer 30 and the carrier plate40.

In FIG. 4C, the example shear force 146 is depicted as being applied tothe carrier plate 40, while the wafer 30 is inhibited from moving in thesame direction by a stop structure 144 engaging an edge 142 of the wafer30. Examples of debonding apparatus having such features are describedherein in greater detail

While such a configuration is also possible with a carrier plate that isgenerally same sized (diameter) as a wafer, tolerance requirements forthe stop structure 144 and positioning of the wafer-carrier assembly canbe much more stringent. For example, if the stop structure is too tallrelative to the carrier plate, the carrier plate's edge can also bestopped from moving.

As shown in FIG. 4C, the carrier plate having a larger lateral dimension(e.g., diameter) can provide more flexibility in the stop structure'sdimensions. For example, even if the stop structure 144 is tall relativeto the wafer (and adhesive layer) thickness, the stop structure 144 isinhibited from moving past the inner surface of the carrier plate 40when the wafer's edge 142 is positioned for separation. Accordingly, thecarrier plate 40 can move laterally in response to the applied shearforce 146.

FIG. 4D shows that in certain implementations, a mechanical force forseparating the wafer 30 from the carrier plate 40 can be in the form ofa pulling force (arrow 156) applied to the wafer 30. Such a force canhave a component that is perpendicular to a plane defined by the wafer30. As the pulling force 156 pulls on the wafer 30, the carrier plate 40is inhibited from moving in the same direction by one or more stopstructures 154 engaging the wafer-side surface of the carrier plate 40at the peripheral portion extending beyond the wafer's edge. Examples ofdebonding apparatus having such features are described herein in greaterdetail.

In certain implementations, the pulling force 156 can be provided by avacuum applied from the wafer side. In other implementations, othernon-vacuum-based pulling forces can also be utilized.

In the example configuration shown in FIG. 4D, the extended dimension ofthe carrier plate 40 (relative to the wafer dimension) allows thecarrier plate 40 itself to act as a substantially stationary anchorwhile the wafer 30 is being pulled away. Accordingly, a carrier platecan be provided for holding a wafer to be temporarily bonded thereto,where the plate's planar dimension is larger than the wafer's planardimension. In the context of circular wafers, circular shaped carrierplates can be provided.

In certain embodiments, such a circular carrier plate can have adiameter that is greater than the wafer's diameter by 1% or more, 2% ormore, 3% or more, 4% or more, 5% or more, 6% or more, 7% or more, 8% ormore, 9% or more, 10% or more, 11% or more, 12% or more, 13% or more,14% or more, 15% or more, 16% or more, 17% or more, 18% or more, 19% ormore, 20% or more, 21% or more, 22% or more, 23% or more, 24% or more,or 25% or more. Thus, for providing carrier functionality for 100-mmwafers (sometimes referred to as 4-inch wafers), a circular carrierplate can have a diameter that is approximately 101 mm or more, 102 mmor more, 103 mm or more, 104 mm or more, 105 mm or more, 106 mm or more,107 mm or more, 108 mm or more, 109 mm or more, 110 mm or more, 111 mmor more, 112 mm or more, 113 mm or more, 114 mm or more, 115 mm or more,116 mm or more, 117 mm or more, 118 mm or more, 119 mm or more, 120 mmor more, 121 mm or more, 122 mm or more, 123 mm or more, 124 mm or more,or 125 mm or more. For providing carrier functionality for 150-mm wafers(sometimes referred to as 6-inch wafers), a circular carrier plate canhave a diameter that is approximately 151.5 mm or more, 153 mm or more,154.5 mm or more, 156 mm or more, 157.5 mm or more, 159 mm or more,160.5 mm or more, 162 mm or more, 163.5 mm or more, 165 mm or more,166.5 mm or more, 168 mm or more, 169.5 mm or more, 171 mm or more,172.5 mm or more, 174 mm or more, 175.5 mm or more, 177 mm or more,178.5 mm or more, 180 mm or more, 181.5 mm or more, 183 mm or more,184.5 mm or more, 186 mm or more, or 187.5 mm or more. Similarly,circular carrier plates for bonding 200-mm, 250-mm, 300-mm, and othersized wafers thereto can be dimensioned accordingly.

In certain embodiments, the foregoing carrier plates can be formed from,for example, sapphire, borosilicate (sometimes referred to as Pyrex),quartz, glass (e.g., SCG72), and other relatively rigid and chemicalresistant materials. In certain embodiments, such carrier plates can beoptically transparent so as allow viewing of the bonded side of thewafer.

FIGS. 5-7 show non-limiting examples of apparatus that can be configuredto separate wafers from carrier plates by shear force in manners similarto the separation mode described in reference to FIG. 4C. In FIG. 5, twoexample debonding apparatus 160 and 170 are shown. The first apparatus160 is depicted as having a base 162 and a sliding member 164.Similarly, the second apparatus 170 is depicted as having a base 172 anda sliding member 174.

The first base 162 can include a plate 166 that has a top surface 168,and defines first and second recesses 180, 200 on the top surface 168.The first recess 180 is at least partially defined by a wall 182 havinga first height. In the example shown, the wall 182 includes a curvedportion that extends approximately as a half-circle; and the radius ofsuch a circle can be selected such that the first recess 180 can receivea wafer to be separated. The first height of the wall 182 can depend onwhether the radius of the first recess 180 accommodates the wafer butnot the corresponding over-sized carrier plate, or both the wafer andthe carrier plate (wafer-sized or over-sized). For the former case, thefirst height of the wall 182 can be greater than the thickness of thewafer due to the over-sized carrier plate as explained in reference toFIG. 4C. For the latter case, the first height of the wall 182 can beselected to be less than the distance between the bottom (unbonded)surface of the wafer to the bonded surface of the carrier plate.

To separate the wafer from its carrier plate, the wafer-carrier assemblyis positioned on the first recess 180 so that the wafer is on thebottom. Such a wafer-carrier assembly can be heated prior to suchpositioning so as to soften the adhesive for easier separation.Alternatively, the recess 180 can be configured to provide heat when thewafer-carrier assembly is positioned thereon. Such a heatingfunctionality can be achieved by, for example, providing a hotplate thatdefines the bottom of the recess 180, or by having the bottom of therecess be in thermal contact with a heat source.

Referring to FIG. 5 and FIG. 6 (showing an underside 262 of the firstsliding member 164), the first base 162 is depicted as having sides 186that define guide slots 188 dimensioned to receive and guide the sideedges 260 of the sliding member 164. In certain embodiments, the guideslots 188 can be dimensioned to guide the sliding member 164 along adirection that is substantially parallel to a plane defined by thewafer-carrier assembly positioned on the first recess 180.

In certain embodiments, the portion of the sliding member 164 thatengages and pushes the edge of the carrier plate is positioned anddimensioned to make such an engagement but does not engage the wafer. Asshown in FIG. 6, such a carrier plate-engaging portion of the slidingmember 164 can be provided by a wall 266 of a recess 264 formed on theunderside 262. The recess 264 and its wall 266 can be dimensioned toreceive the carrier plate when the side edges 260 are positioned in theguide slots 188, but not the wafer.

Upon such positioning of the sliding member 164 on the wafer-carrierassembly, the sliding member 164 can be pushed (e.g., towards the leftin FIG. 5) to provide a shear force to the lagging edge of the carrierplate. Since the leading edge of the wafer is inhibited from moving bythe wall 182 of the first recess 180, the carrier plate slides away fromthe wafer by the guided motion of the sliding member 164. In certainembodiments, a handle 252 can be provided on the upper side of thesliding member 164 to facilitate application of the shear force.

In certain embodiments, the sliding member 164 can be provided with anopening 254 to allow viewing of the carrier plate during the separationprocess. In embodiments where the carrier plate is opticallytransparent, the wafer can also be viewed through the opening 254.

Referring to FIG. 5, the second recess 200 formed on the top surface 168can be dimensioned to receive the carrier plate that has been separatedby the sliding motion of the sliding member 164. In certain embodiments,the second recess 200 is sufficiently dimensioned in lateral dimensionand depth so as to allow the carrier plate to readily fall therein andbecome clear of the underside 262 of the sliding member 164.

In certain embodiments, the first base 162 can include a number offeatures that can facilitate various operations during the debondingprocess. For example, cutouts 190 can be provided along the sides 186 soas to facilitate positioning of the wafer-carrier assembly onto therecess 180, and to facilitate removal of the separated wafer from therecess 180. In another example, to accommodate a wafer handling tool(not shown) during such removal, a deeper recess 184 can be formed atthe edge of the first recess 180 so as to allow handling of the wafervia its bottom (unbonded) surface (e.g., using a vacuum wand).Similarly, a deeper recess 202 can be formed at the edge of the secondrecess 200 so as to allow easier removal of the carrier plate. In yetanother example, the ends 192, 194 of the sides 186 that define theguide slots 188 can be rounded or angled so as to allow easier insertionof the sliding member 164 into the guide slots 188.

Referring to FIG. 5, the base 172 of the second debonding apparatus 170is depicted as having first and second recesses 210, 230, and guideslots 218 for receiving and guiding the sliding member 174. Variousdimensions and functionalities provided by such features can be similarto those described in reference to the first example debonding apparatus160.

In certain embodiments, however, the first recess 210 of the base 172can be configured to provide suction to the wafer when the wafer-carrierassembly is positioned thereon. Such suction can be facilitated byfeatures 220 such as grooves and/or holes formed at the bottom surfaceof the recess 210, where such features are in communication with avacuum system (not shown). In the example shown, the features 210include a number of concentric circular grooves that can facilitatedistributing of the suction force on the wafer.

Holding of the wafer in such a manner provides an additional resistanceagainst lateral movement of the wafer during the sliding separation ofthe carrier plate. In certain embodiment, the depth of the recess 210can be selected so that when the wafer is vacuum-held in the recess 210,the bonded side of the carrier plate is above the top of the recess 210so as to allow the carrier plate to slide upon application of a shearforce by the sliding member 174.

FIGS. 5 and 7 show that in certain embodiments, the sliding member 174can include some features that are different than the sliding member 164of the first debonding apparatus 160. For example, the length of thesecond sliding member 174 is considerably shorter than that of the firstsliding member 164. To accommodate such a shorter length, a handle 272can be positioned forward of a carrier plate-engaging feature of thesliding member 174. In FIG. 7, such a carrier plate-engaging feature isdepicted as being provided by a wall 286 of a recess 284 formed on theunderside 282 of the sliding member 174.

FIGS. 8-10 show examples of an apparatus that can be configured toseparate wafers from carrier plates by a pulling force applied to awafer in manners similar to the separation mode described in referenceto FIG. 4D. FIG. 8 shows a perspective view of an example debondingchuck 300 that can be configured to provide such wafer-separatingfunctionality. FIGS. 9A and 9B show sectional side view and plan view,respectively, of the debonding chuck 300. FIGS. 10A-10E show an examplesequence of a wafer being separated from a carrier plate.

The example debonding chuck 300 is described herein in the context ofseparating a circular wafer from a circular carrier plate. It will beunderstood, however, that one or more features or concepts describedherein can also be implemented in other shaped wafers and carrierplates. Further, such features and concepts can also be implemented inother situations not necessarily involving semiconductor wafers.

In certain implementations, a wafer-carrier assembly to be separated canbe lowered onto the debonding chuck with the wafer on the lower side.Accordingly, the debonding chuck 300 can define a recess 306 (with adiameter D) having a floor surface 314 and a side wall 316 (with aheight H). The recess 306 is depicted as being formed relative to anupper surface 304.

In certain embodiments, the diameter D of the recess 306 can be selectedto allow the recess 306 to receive the wafer but not the oversizedcarrier plate. The upper surface 304 can be dimensioned to allow theperipheral portion of the lower surface of the carrier plate not coveredby the wafer to be supported thereon when the wafer is in the recess306.

In certain embodiments, the height H of the side wall 316 can beselected to allow the recess 306 to receive the wafer that is yetunseparated from the carrier plate and to provide space between thebottom (unbonded) side of the wafer and the floor surface 316 of therecess 306. The vertical dimension of such a space can be selected suchthat the wafer, once separated and resting on the floor surface 316, issufficiently separated from the carrier plate to allow easy removal ofthe carrier plate. The vertical dimension of the space can also beselected to limit deformations (e.g., flexing) of the wafer as the waferis being pulled away from the carrier plate. An example of suchwafer-flexing is described in greater detail in reference to FIG. 10.

In certain implementations, at least some of the foregoing designcriteria can be addressed by a recess diameter D that is greater thanthe diameter of a wafer but less than the diameter of a carrier plate.For the wafer-plate example where the wafer's diameter is approximately100 mm and the carrier plate's diameter is approximately 110 mm, therecess diameter D can be in a range of about 101 mm to 108 mm, about 101mm to 106 mm, or about 101 mm to 104 mm. In certain embodiments, therecess diameter D can be approximately 102 mm for the foregoing example.

For the wafer-plate example where the wafer's diameter is approximately150 mm and the carrier plate's diameter is approximately 160 mm, therecess diameter D can be in a range of about 151 mm to 158 mm, about 151mm to 156 mm, or about 151 mm to 155 mm. In certain embodiments, therecess diameter D can be approximately 152 mm for the foregoing example.

In certain implementations, at least some foregoing design criteria canbe addressed by a recess depth H that is greater than the thickness of awafer. In certain embodiments, the depth H can be selected to be greaterthan the wafer thickness and less than about five times the waferthickness, about four times the wafer thickness, about three times thewafer thickness, or about two times the wafer thickness.

For the wafer-plate example where the wafer's thickness is approximately100 μm, the recess depth H can be selected to be greater than thethickness by an amount in a range of about 0.001″ to 0.002″(approximately 25 μm to 50 μm). Thus, in certain embodiments, a recessdepth H of about 140 μm can be utilized.

In the example shown, the recess 306 is depicted as generally having acylindrical shape with the side wall 316 being generally perpendicularto the floor surface 314. It will be understood, however, that such arecess shape is not a requirement. For example, the side wall 316 can beangled away from the perpendicular orientation, and yet allow theseparated wafer to engage the floor surface 314 while the carrier plateremains supported by the upper surface 304.

Referring to FIGS. 8 and 9, the floor surface 314 of the recess 306 candefine one or more features for applying suction to the recess 306 suchthat the suction can pull the wafer away from the carrier plate. Theoversized carrier plate itself, being positioned above the recess 306and supported by the upper surface 304, acts as a relatively rigid andstationary anchor that facilitates the suction-induced movement of thewafer towards the floor surface 314. Accordingly, the wafer becomesseparated from the carrier plate.

In certain embodiments, the suction provided to the recess 306 can bedistributed along the floor surface 314 so as to reduce likelihood of ahighly localized suction that can damage a wafer. In the example shownin FIGS. 8 and 9, a number of grooves 308 formed on the floor surface314 are shown to be in communication with a number of holes 310 that arein turn in communication with a vacuum device such as a pump (not shown)through vacuum pathways 312. The example grooves 308 are depicted asincluding a number of concentric grooves 308 a and a number of radiallyextending grooves 308 b. The example holes 310 are depicted as beingpositioned approximately at the center and at about 90 degrees along theouter circumference of the outer circular groove 308 a. In such aconfiguration, suction formed at the holes 310 can be distributed alongthe floor surface 314 of the recess 306.

It will be understood that a number of different configurations ofholes, grooves, and/or other features can be provided to distribute thesuction in the recess. For example, a floor surface can have a number ofholes (and no grooves) arranged in a desired pattern along the floorsurface. In another example, a number of grooves can be formed so as tobe in communication with one or more vacuum pathways that are notnecessarily below the floor surface. In yet another example, a number ofgrooves does not necessarily need to include both the concentric typeand the radially extending type. In yet another example, the groovesneed not even be symmetric. A number of other configurations arepossible.

It will also be understood that, although the recess portion and theportion having the vacuum pathways are depicted as being part of asingle piece, such depiction is for illustrative purpose. Such astructure having the recess portion and the vacuum pathways can beimplemented by one or more pieces in a number of ways.

In certain embodiments, for example, a debonding chuck can include abottom plate that defines the floor surface and the grooves and holes,but not the vacuum pathways. Such a bonding chuck can then be installedon a platform so as to allow suction communication between the holes andone or more vacuum pathways.

In certain embodiments, a debonding chuck having one or more of theforegoing features can be fabricated from metal or other resilientmaterials. For example, a debonding chuck can be fabricated from metalsuch as aluminum which is relatively easy to machine. Featuresassociated with the example shown in FIGS. 8 and 9 are relatively simplefor the purpose of machining, thereby further facilitating efficientfabrication.

In certain embodiments, a debonding chuck can act as a hotplate or be inthermal communication with a heat source so as to allow heating of awafer-carrier assembly positioned thereon. For such embodiments,materials such as aluminum can be appropriate. In other embodiments, adebonding chuck does not have a heating capability; thus, awafer-carrier assembly can be heated prior to being positioned on thechuck.

FIGS. 10A-10E shows an example wafer separation sequence that can beachieved using the wafer chuck 300 described in reference to FIGS. 8 and9. FIG. 10A shows a stage 320 where suction (arrows 326) is beingapplied to a wafer-carrier assembly (a wafer 30 and a carrier plate 40with a softened adhesive layer 38 therebetween) placed on the recess306, so that the wafer 30 is in the recess 306 and the carrier plate 40is supported by the upper surface 304. The suction in the recess 306 isdepicted as being in communication (dashed lines 324 and arrow 322) witha vacuum device (not shown).

FIG. 10B shows a stage 330 where the edge portion of the wafer 30 isdepicted as being separated from the carrier plate 40 due to thesuction. In debond chuck configurations where the suction is distributedalong the floor surface of the recess, such initial separation of theedge, is likely due to the surface tension (provided by the meltedadhesive) ending at the edge. Thus, the edge portion generally has alower surface tension per area than at inward areas.

FIG. 10C shows a stage 340 where the wafer separation continues inward.In FIG. 10C, the edge of the wafer 30 is depicted as having reached andengaging the floor surface of the recess 306.

FIG. 10D shows a stage 350 where the wafer 30 has been separated fromthe carrier plate 40 and is resting on the floor surface of the recess306. Once such a stage is reached, the suction can be stopped.

FIG. 10E shows a stage 360 where the suction has stopped and the carrierplate removed. Accordingly, the separated wafer 30 with at least some ofthe adhesive 38 remaining thereon can be removed (arrow 362) forcleaning. Such removal of the wafer 30 can be achieved in a number ofways, depending on whether the debonding chuck is part of a manualsystem or an automated system.

FIGS. 11 and 12 show non-limiting examples of ways in which one or morefeatures associated with the debonding chuck described in reference toFIGS. 8-10 can be implemented in systems, and how such features can bemodified to provide desired functionalities. FIG. 11A shows an exampledebonding system 370 having a debonding chuck component 371. Such achuck can include some or all of the features described herein inreference to FIGS. 8-11.

In certain implementations, the system 370 can further include one ormore sensors (component 374) that are configured to sense one or moreoperating conditions of the system 370. For example, the system 370 caninclude a heating component 376 configured to heat the wafer-carrierassembly so as to melt the adhesive layer. For such a component, atemperature sensor can be provided so as to monitor the temperature ofthe wafer-carrier assembly. In another example, the system can include avacuum component 378 configured to provide the suction to the recess ofthe debonding chuck. For such a component, a pressure sensor can beprovided so as to monitor the pressure associated with the suction beingprovided to the recess.

In certain implementations, the system 370 can further include a controlcomponent 372 configured to control one or more operations associatedwith the debonding process. In automated systems, the control component372 can be configured to coordinate various operations, such as loadingof the wafer-carrier assembly on the chuck, heating the wafer-carrierassembly, separating the wafer from the carrier plate, removing thecarrier plate, removing the wafer from the chuck, and other relatedoperations.

FIG. 11B shows an example of how the control component 372 can controlthe operation of the heating component 376. For the purpose ofdescription, it will be assumed that heating occurs via the debondingchuck, and that when a new wafer-carrier assembly is loaded on thechuck, the assembly's temperature is lower than the target temperaturewhere the adhesive layer melts.

Thus, in FIG. 11B, the temperature of the wafer-carrier assembly isdepicted as increasing as heat is applied. Such temperature measurementscan be provided by the sensor component 374, and can be achieved in anumber of ways. For example, the wafer-carrier assembly's temperaturecan be estimated based on the measured temperature of the hotplate,taking into account time needed for the wafer-carrier assembly reachequilibrium with the hotplate. In another example, an externaltemperature probe positioned above the wafer-carrier assembly can taketemperature measurements in a number of different ways.

When a target temperature T2 is reached, the control component 372 canissue a signal to stop further heating, and to initiate the waferseparation process. Such a separation process can include the vacuumcomponent providing suction to the recess. At such a stage, pressure inthe recess can begin an initial value and decrease as suction isapplied.

FIG. 11C shows an example pressure profile as the separation processprogresses. Such pressure measurements can be provided by the sensorcomponent 374 and be achieved in a number of know ways.

As suction is applied to the recess and the wafer is being pulled at,the associated pressure is depicted as being at or about a levelindicated as 382. As the wafer is separated and displacing the lowerportion of the recess, the associated pressure is depicted as changing(384) so as to reach a new level indicated as 386. During such apressure change (e.g., drop in pressure) can be detected, and anappropriate command can be issued by the control component 372 so as tostop the suction.

As described herein, a number of features such as grooves and/or holescan be provided to the floor surface of the recess so as to distributethe suction's pulling force applied to the wafer. Such distribution andmagnitudes of the distributed pulling forces can be adjusted by thesize, density, and pattern of such features, as well as the strength ofthe overall suction being provided.

The suction strength as applied to the wafer can also be influenced byhow well the carrier plate engages with the upper surface of thedebonding chuck and “seals” the recess. For example, the upper surface304 shown in FIG. 9B can extend around the recess 306. Thus, a tightcontact between the carrier plate and the upper surface 304 can resultin the recess 306 being evacuated relatively quickly, even if thesuction strength can be controlled.

Similarly, the suction strength as applied to the separated wafer canalso be influenced by how well the wafer engages with the floor surfaceof the recess and “seals” the recess from the vacuum pathways. In theexample shown in FIGS. 9B and 10D, the wafer 30 can cover substantiallyall of the grooves and holes on the floor surface 314. Thus, a tightcontact between the wafer and the floor surface 314 can result in thepressure differential increasing sharply between the regions above andbelow the wafer.

In certain implementations, such good “seals” may not be desirable,since they can increase the likelihood of damage to the wafer-carrierassembly (before separation) and the wafer (after separation). Thus, incertain embodiments, one or more portions of the recess 306 can be opento the outside by, for example, one or more openings on the side wall.Such opening(s) on the side wall can be dimensioned to limit thepressure differential between the regions above (outside) and below(recess 306) the wafer-carrier assembly. Such opening(s) can alsofacilitate loading of the wafer-carrier assembly, and removal of thecarrier plate after separation in certain implementations.

Similarly, in certain embodiments, at least some of thesuction-distributing features (such as grooves) can be exposed to theoutside. Such an exposure of the grooves can be configured to limit thepressure differential between the regions above (recess 360) and below(grooves 308) the wafer. Such opening(s) can also facilitate removal ofthe separated wafer in certain implementations.

FIGS. 12A and 12B show an example debonding chuck 390 configured toprovide both of the foregoing pressure relief features. The chuck 390 isgenerally similar to the example chuck 300 described in reference toFIGS. 8 and 9. However, the chuck 390 is depicted as having an angledsurface 392 on one portion of the perimeter. The angled surface 392 canbe dimensioned to cut through a portion of the side wall (the cutportion depicted as dotted side wall 316 in FIG. 12B), and through aportion of the peripheral portions of the grooves 308 a, 308 b.

Accordingly, the angled surface 392 allows provides at least somepressure communication between the outside and the recess 306 (indicatedas arrow 394 a) and between the outside and the grooves 308 a, 308 b(indicated as arrows 394 c, 394 b). In certain embodiments, more thanone of such pressure relief opening sets can be provided. In certainembodiments, openings for the vacuum pathways and the recess can beprovided separately at different locations.

In certain implementations, one or more features associated with thevarious embodiments of the debonding chuck described in reference toFIGS. 8-12 can be implemented in a number of debonding systems. FIGS.13A and 13B show various components of an example of a manual debondingsystem. FIGS. 14-16 show various devices that can facilitate efficienthandling of wafers from the manual system and cleaning of such wafers.FIGS. 17-20 show various components of an example automated debondingsystem.

Referring to FIGS. 13A and 13B, a debonding apparatus 500 includes adebonding chuck 502 mounted on a hotplate 504. The chuck 502 can includeone or more features as described in reference to FIGS. 8-12. Theparticular example chuck shown in FIG. 13A includes an angled surfacefeature 512 described in reference to FIGS. 12A and 12B.

The debonding apparatus 500 can also include a vacuum system (e.g.,vacuum pathway 506) configured to provide the suction for separatingwafers from carrier plates. The apparatus 500 is shown to include avacuum control switch 510 for turning the vacuum system on and off, anda heating control 508 that can set the hotplate temperature.

In the example shown, loading of the wafer-carrier assembly and removalof the separated carrier plate and wafer can be performed manually by anoperator. Turning on and off of the vacuum can also be performedmanually.

Also shown in the example, the hotplate can remain heated at a desiredtemperature (e.g., approximately 130° C. to 170° C.). To facilitate ahigher throughput, wafer-carrier assemblies to be debonded can bepreheated by a separate heater 530. In FIG. 13A, a wafer-carrierassembly 520 is shown as being preheated by the heater 530. In FIG. 13B,the preheated assembly 520 is shown as having been transferred from theheater 530 to the debonding chuck 502 of the apparatus 500, and ready tobe debonded.

An example sequence of operations for preheating and debonding can beperformed as follows. A wafer-carrier assembly 520 to be preheated canbe positioned on the heater 530 with the wafer underneath the carrierplate. Once preheated, the assembly 520 can be transferred to thedebonding chuck 502 of the apparatus 500 in the same orientation.

Once on the chuck 502, the wafer can be separated from the carrierplate. The separated carrier plate can be removed first since it is onthe top; and the wafer in the recess of the chuck 502 has its adhesiveside facing up. The wafer can be removed from the chuck 502 andpositioned on a wafer holder while in the same orientation for cleaning.Thus, one can readily see that the top-loading capability of the chuckand the chuck not requiring any additional devices on its top for theseparation process allows the manual sequence of operations to beperformed easily, relatively fast, and with lowered risk of damage tothe wafer. As described herein, such features of the debonding chuckallow the debonding operation steps to be automated.

FIGS. 14A-14C show various views of a wafer holder 600 configured toallow the separated wafer (30) from the debonding apparatus 500 to becollected for handling during post-separation processes such ascleaning. FIGS. 15A and 15B show a cassette 650 configured to receive aplurality of wafer holders (600) with wafers thereon. The cassette 650can be in a first orientation (FIG. 15A) in which the cassette 650 isconfigured to receive the wafer holders 600 with debonded wafers. Thecassette 650 can also be in a second orientation (FIG. 15B) in which thecassette 650 is configured to hold the wafer holders 600 (and hence thewafers) at a desired angle relative to the vertical direction tofacilitate efficient cleaning and drying of the wafers.

Referring to FIGS. 14A-14C, the wafer holder 600 can include a plate 602having a first surface 612. The plate 602 can be dimensioned toaccommodate a debonded wafer 30, and can include a handling tab 604. Inthe example shown, the tab end of the plate 602 has a generally straightedge and square corners; while the end 610 opposite from the tab 604 iscurved to generally conform to the wafer's circular shape. FIG. 14Cshows a wafer 30 held by the holder 600. As described in the examplesequence of manual debonding operations, a debonded wafer can have itsadhesive side on top. Thus, the upper side of the wafer 30 shown in FIG.14C is the adhesive side.

Referring to FIG. 15A, the wafer holder 600 with the wafer 30 heldtherein is shown to be inserted into one of the plurality of receivingslots in the cassette 650 (in its first orientation). In such aconfiguration, the adhesive side (to be cleaned) of the wafer 30 remainson the top, thereby facilitating an efficient transfer of wafers betweenthe various operations.

Referring to FIGS. 14A-14C, the wafer holder 600 can further include a“J” shaped (plate 602, a second extension 614 from the plate 602, and asecond extension 616 from the first extension 614) retaining feature 608formed at or near the curved end 610 opposite from the tab end. Theretaining feature 608 thus defines a recess dimensioned to receive anedge of the wafer 30.

In the example shown there are two retaining features 608 separated by aplain edge (of the plate 602) in between and generally centered at thecurved end 610. Such a separation of the retaining features 608 allowsliquid such as cleaning fluid to drain from the retaining features 608when the curved end is downward of the tab end (e.g., FIG. 15B).

Referring to FIGS. 14A-14C, the wafer holder 600 can further include anumber of bumps 606 formed on the first surface 612 of the plate 602. InFIG. 14B, the bumps 606 are shown to engage the unbonded side of thewafer 30, so as to separate the wafer from the first surface 612 of theplate 602. Such a separation inhibits the wafer surface from sticking tothe first surface (e.g., due to surface tension of fluid therebetween),and to promote drainage of fluid. The retaining feature 608 can bedimensioned to accommodate the wafer offset provided by the bumps 606.The bumps 606 can be configured to have smooth surfaces so as to reducethe likelihood of damage to the wafer 30.

In certain embodiments, the wafer holder 600 can be formed fromrelatively rigid and chemical resistant materials such as quartz andglass. In certain embodiments, the wafer holder 600 can be formed fromone of the foregoing materials by a process such as molding.

Referring to FIGS. 15A and 15B, the cassette 650 is shown to have agenerally rectangular box shaped structure formed by frame members 652.To allow flow of cleaning liquid to the wafers, the six faces of the boxare generally open. The side (656) through which the wafer holders areloaded is substantially free of structures other than the box-definingframe members 652. From the sides of the loading side 656 extend anumber of slot-defining bars 654 to the side opposite from the loadingside 656. The slot-defining bars 654 are shown to be angled inward tofacilitate more positive wafer-holder retaining slots.

As shown in FIG. 15B, when the cassette 650 is oriented so that theloading side 656 is facing upwards (such as during cleaning anddraining), the slots formed by the bars 654. (and thus the waferstherein) are at an angle away from the vertical. Such an angle can beselected based on a number of operating parameters. For example, if theorientation of the wafer and its holder are closer to vertical, thenfluid drainage improves; however, the wafer is less stable in its holderand full or close to full weight of the wafer can be concentrated on thebottom edge portion of the wafer. On the other hand, if the orientationof the wafer and its holder are more away from the vertical, then thefluid drainage can suffer; however, the wafer is more stable in itsholder and the weight of the wafer is better distributed to the bumps606 of the holder 600.

In certain embodiments, the angle of the slots on the cassette 650 canbe selected to be approximately 20 degrees relative to the vertical. Incertain embodiments, such an angle can be in a range of approximately 5to 45 degrees from the vertical; approximately 10 to 30 degrees from thevertical; or approximately 15 to 25 degrees from the vertical.

In embodiments where the slots on the cassette 650 are angled in theforegoing manner, if the cassette 650 is positioned on a flat surface sothat the loading side 656 faces the operator, the wafers can slide outdue to the now-downward angle of the slots. Thus, a base unit 660 can beprovided (FIG. 15A), where the base 660 includes an angledcassette-holding surface. In certain embodiments, the angled surface ofthe base 660 can be selected to counter the downward angle of the slots,such that the wafers in the slots can be generally horizontal duringcollection from the debonding apparatus.

In certain embodiments, the cassette 650 can be formed from relativelyrigid and chemical resistant materials such as quartz and glass.

In certain implementations, a cassette (650) that has been filled withwafers (on their holders) can be dipped into one or more solvent tanksto clean the wafers (e.g., by acetone) in known manners. Once cleaned,the cassette (650) can be removed from the solvent tanks and be placedin an oven to dry the wafers. During such cleaning and drying, thecassette (650) can be in the orientation shown in FIG. 15B so as toorient the wafers at an angle.

In certain implementations, such solvent-cleaned and dried wafers can beash plasma cleaned to remove residues that may remain. FIG. 16 shows acassette 670 that is similar to the cleaning cassette 650 of FIG. 15.

More particularly, the cassette 670 is shown to have a generallyrectangular box shaped structure formed by frame members 672. To allowash plasma cleaning of the wafers in a generally uniform manner, thefour sides (including the loading side 676) are generally open so as toprovide similar exposure for the spaced layers of wafers. Unlike thecleaning cassette 650, the top portion of the ashing cassette 670includes a cover 678 that is shaped similar to a wafer holder (600 inFIG. 14). Thus, the top wafer positioned in the cassette 670 also has awafer holder-like cover above, like the rest of the wafers. Unlike thecleaning cassette 650, the ashing cassette 670 generally remains in oneorientation; thus, the slots (defined by the slot-defining bars 674) forholding the wafer-holders do not need to be angled. In certainembodiments, such slots are configured so that the wafers are heldgenerally horizontally during the ash plasma cleaning process.

Referring to FIG. 17, an automated debonding system 700 can include anumber of stations that can perform similar debonding and cleaningoperations associated with the manual debonding apparatus 500 of FIG.13. The automated system 700 is shown to include a debonding station710, a cooling station 720, and a cleaning station 730. The system 700is also shown to include a robotic component 740 that controls themovements and manipulating operations of one or more robotic arms (e.g.,742, 744). Operations of robotic component 740 to manipulate and movewafer-carrier assemblies, carrier plates, and wafers can be achieved ina number of known manners.

Referring to FIGS. 18A and 18B, the debonding station 710 includes adebonding chuck 800 having one or more features as described herein. Thedebonding chuck 800 is shown to be mounted on a platform 802.

In the example automated system 700, the debonding station 710 caninclude a heating component (not shown) so as to allow heating of awafer-carrier assembly 804 via the chuck 800. The debonding station 710can also include or be in communication with a vacuum system (not shown)so as to facilitate the separation of the wafer-carrier assembly 804 viathe chuck 800.

To position the wafer-carrier assembly 804 on the debonding chuck 800,the assembly 804 is positioned (via the robotic component 740) on thereceiving portions of a number of lifting pins 810 that are positionedcircumferentially outside the chuck's recess. The receiving portions ofthe lifting pins 810 can be at similar radial location as that of theupper surface of the recess, so that when the pins are lowered, theirreceiving portions are at the same or lower level than the upper surfacewhere the carrier plate rests. As shown in FIG. 18B, the upwardextending members positioned radially outward of the receiving portionsof the lifting pins 810 generally constrains the lateral position of thecarrier plate over the upper surface of the recess.

Referring to FIG. 18B, the wafer-carrier plate 804 positioned on thepins 810 can be lowered to the chuck 800; and heating and separation ofthe wafer can occur. Once the wafer is separated from the carrier plate,the separated carrier plate can be lifted back up by the lifting pins810. Then, the carrier plate can be moved away from the debondingstation 710 via the robotic component 740; and the lifting pins 810 canbe lowered back into the platform 802.

In certain embodiments, the lowering and/or lifting of each of thelifting pins 810 can be controlled independently. Such a capability canreduce the likelihood that the wafer will also be lifted when thecarrier plate is lifted. Such a likelihood can be greater when all ofthe pins rise at substantially the same time. By raising one pin first,the carrier plate can be further separated or peeled away from the waferso as to keep the wafer held to the vacuum surface of the chuck 800.

Once the carrier plate has been removed and the lifting pins 810retracted, the separated wafer can be removed from the recess of thedebonding chuck. In the example shown, the wafer can be lifted out ofthe recess by an upward suction applied by a suction lifting member 760.Note that the lifting member 760 positioned over the chuck 800 for thepurpose of lifting the wafer; and remains away from the chuck duringother operations.

Once the wafer is lifted above the chuck 800, the wafer can betransferred to a robotic arm (e.g., 744) that in turn positions thewafer on the cooling station 720. Once the wafer has cooledsufficiently, the wafer is transferred (via the robotic component 740)to the cleaning station 730 to remove the adhesive.

Referring to FIG. 19, the cleaning station 730 can be configured toprovide both cleaning and drying functionalities. The cleaning can beachieved by cleaning solvent (e.g., acetone) sprayed through a sprayhead 824 on a swivel arm. The swivel arm allows the solvent spray tosweep across the wafer.

In the example shown, a chuck 822 is provided for holding the waferduring the foregoing cleaning process, and for spinning and drying thewafer. To provide a strong hold of the wafer during such spinning, thechuck 822 can be configured to be relatively large and to hold the waferby vacuum.

In the example shown, the chuck 822 is in a raised position to receive awafer. Once the wafer is secured thereon, the chuck 822 can be loweredinto a space surrounded by a housing 820. The housing 820 can bedimensioned to capture fluids during the cleaning process, and tocontain fluids being spun away from the wafer during the drying process.

Spray cleaning in the foregoing manner in the automated system 700 hasshown to clean the wafers better than the solvent dipping method usedafter the manual debonding process. In the through-wafer via process onGaAs wafers, the spray cleaning can result in an increase in the overallyield.

FIG. 20 shows an example of how the separated carrier plates and thecleaned wafers can be collected in the automated debonding system 700. Acarrier plate-holding receptacle 830 is depicted as holding a pluralityof carrier plates 40 that have been separated from their respectivewafers. Once filled, the receptacle 830 can be removed from the system700 for recycling of the carrier plates 40.

FIG. 20 also shows a wafer receptacle 840. The receptacle 840 can beconfigured to hold a plurality of support plates 842 such as thosecommercially available Gel-Pak plates. Each support plate 842 holds onecleaned wafer; and once the receptacle 840 is filled, the receptacle canbe removed from the system 700.

In certain implementations, the wafers removed from the automated system700 can be cleaned further via the ash plasma cleaning process. For sucha cleaning process, the wafers can be transferred from the Gel-Paksupport plates 842 onto the wafer holders (600) described in referenceto FIG. 14. Such holders with wafers thereon can be loaded onto thecassette 670 of FIG. 16 for the ash plasma cleaning process.

In various implementations, the wafers debonded and cleaned in variousmanners described herein can be collected for further processing such astesting and singulation.

Referring to FIGS. 18A and 18B where the example lifting pins 810 aredepicted, it is noted that in certain implementations, a debondingapparatus having such a set of lifting pins can include a chuck with avacuum surface that may or may not be recessed. If the vacuum surface isrecessed, the depth of such a recess may or may not by greater than thethickness of a wafer placed therein.

Thus, even if there is no recess or the thickness of the wafer isgreater than the depth of the recess, the wafer can be vacuum held bythe vacuum surface and a relatively rigid carrier plate can be moved orpeeled away from the substantially stationary wafer by appropriateraising of lifting members (e.g., lifting pins). For example, by raisingone lifting member first, the carrier plate can be separated or peeledaway from the wafer while the wafer is held to the vacuum surface.

In certain embodiments, one or more of the foregoing features can beimplemented in a debonding apparatus (manual or automated) that can beconfigured to separate a wafer from a plate. In certain embodiments, theplate can have a lateral dimension that is larger than a lateraldimension of the wafer, such that an assembly of the wafer and the plateincludes a peripheral area on the plate that is not covered by thewafer. In certain embodiments, the wafer and the plate can bedimensioned similarly so that there is little or no peripheral area.

Such a debonding apparatus can include a chuck having a vacuum surfaceconfigured to receive the wafer of the assembly. The apparatus canfurther include one or more separation members disposed relative to thevacuum surface so as to allow the one or more separation members toengage at least a portion of the plate and move that portion of theplate without directly touching the wafer. Such a forced motion of theplate (induced by the one or more separation members) allows the plateto separate from the wafer when the wafer is held on the vacuum surfaceby application of vacuum.

In certain embodiments, the one or more separation members can includeone or more lift members. In certain embodiments, such lift members caninclude a a plurality of lift pins (e.g., lift pins 810 of FIG. 18B)dimensioned and disposed so as to engage the peripheral area on theplate but not the wafer. Such lift pins can be configured so that atleast one is capable of moving independently from other lift pin(s).

In certain embodiments, the one or more lift members can include a blade(e.g., a spatula shaped device) dimensioned and disposed so as to engagethe peripheral area on the plate but not the wafer. Such a blade canengage the peripheral area on the plate and lift the plate away from thewafer.

In certain embodiments, the one or more separation members can include asuction member disposed on the side of the plate that is opposite fromthe side engaging the wafer. In such an example, the plate may or maynot be oversized relative to the wafer. The suction member can bedisposed away from the plate's center so as to allow one side of theplate to be separated first from the wafer.

In certain embodiments, the vacuum surface can be defined by a floorsurface of a recess having a lateral dimension that is larger than thelateral dimension of the wafer, but less than the lateral dimension ofthe plate. In certain embodiments, the recess can have a depth that isselected to be greater than the wafer's thickness such that uponapplication of the vacuum, the wafer can be pulled away from the plateby the suction force and allowed to become separated from the plate andengage the vacuum surface of the recess.

In certain implementations, a debonding apparatus having one or more ofthe foregoing features can be implemented in an automated debondingsystem or a manual debonding system.

Unless the context clearly requires otherwise, throughout thedescription and the claims, the words “comprise,” “comprising,” and thelike are to be construed in an inclusive sense, as opposed to anexclusive or exhaustive sense; that is to say, in the sense of“including, but not limited to.” The word “coupled”, as generally usedherein, refers to two or more elements that may be either directlyconnected, or connected by way of one or more intermediate elements.Additionally, the words “herein,” “above,” “below,” and words of similarimport, when used in this application, shall refer to this applicationas a whole and not to any particular portions of this application. Wherethe context permits, words in the above Detailed Description using thesingular or plural number may also include the plural or singular numberrespectively. The word “or” in reference to a list of two or more items,that word covers all of the following interpretations of the word: anyof the items in the list, all of the items in the list, and anycombination of the items in the list.

The above detailed description of embodiments of the invention is notintended to be exhaustive or to limit the invention to the precise formdisclosed above. While specific embodiments of, and examples for, theinvention are described above for illustrative purposes, variousequivalent modifications are possible within the scope of the invention,as those skilled in the relevant art will recognize. For example, whileprocesses or blocks are presented in a given order, alternativeembodiments may perform routines having steps, or employ systems havingblocks, in a different order, and some processes or blocks may bedeleted, moved, added, subdivided, combined, and/or modified. Each ofthese processes or blocks may be implemented in a variety of differentways. Also, while processes or blocks are at times shown as beingperformed in series, these processes or blocks may instead be performedin parallel, or may be performed at different times.

The teachings of the invention provided herein can be applied to othersystems, not necessarily the system described above. The elements andacts of the various embodiments described above can be combined toprovide further embodiments.

While certain embodiments of the inventions have been described, theseembodiments have been presented by way of example only, and are notintended to limit the scope of the disclosure. Indeed, the novel methodsand systems described herein may be embodied in a variety of otherforms; furthermore, various omissions, substitutions and changes in theform of the methods and systems described herein may be made withoutdeparting from the spirit of the disclosure. The accompanying claims andtheir equivalents are intended to cover such forms or modifications aswould fall within the scope and spirit of the disclosure.

1. A wafer holding device, comprising: a plate having a surfacedimensioned to receive a wafer thereon; and a plurality of featuresformed on the surface and distributed along the surface so that thewafer positioned on the surface is in contact with at least some of thefeatures and offset from the surface.
 2. The device of claim 1, furthercomprising one or more wafer-retaining features formed along an edge ofthe plate, the retaining features configured so that when the plate isoriented with the edge downward and the surface facing upward and at anangle away from horizontal, the wafer held thereon engages the retainingfeatures and is inhibited from falling off the plate.
 3. The device ofclaim 2, wherein the one or more wafer-retaining features includes twoJ-shaped hook features on the side of the first surface, the two hookfeatures separated by an open space dimensioned to allow drainage of theliquid.
 4. The device of claim 1, wherein the plurality of featuresinclude a plurality of bumps.
 5. The device of claim 4, wherein each ofthe plurality of bumps includes a curves surface dimensioned to engagethe wafer.
 6. The device of claim 1, wherein the features aredimensioned and distributed to allow efficient movement of liquidrelative to the wafer during cleaning and drying operations.
 7. Thedevice of claim 1, wherein the edge having the retaining features has acurved shape to conform to the curved edge of the wafer.
 8. The deviceof claim 1, wherein the plate defines a handling tab on an edge oppositefrom the edge having the retaining features.
 9. A cassette for holdingone or more of the wafer holding device of claim 1, the cassetteconfigured to be capable of being in collection orientation and acleaning orientation, the cassette further configured so that when inthe collection orientation, the wafer holding device is held in thecassette approximately horizontally, and when in the cleaningorientation, the wafer holding device is held at an angle away from thevertical so that the wafer is retained on the plate.
 10. The cassette ofclaim 9, wherein the angle is in a range of about 5 degree to 45 degreesrelative to the vertical.
 11. The cassette of claim 10, wherein theangle is in a range of about 10 degrees to 30 degrees relative to thevertical.
 12. The cassette of claim 11, wherein the angle is in a rangeof about 15 degrees to 25 degrees relative to the vertical.
 13. Thecassette of claim 11, wherein the angle is about 20 degrees relative tothe vertical.
 14. A cassette for holding one or more of the waferholding device of claim 1, the cassette configured so the wafer holdingdevice is held in the cassette approximately horizontally to allowplasma cleaning of a wafer held on the wafer holding device.
 15. Thecassette of claim 14, further including a top cover disposed above alocation where the uppermost wafer holding device is held, the top coverdimensioned to provide a cover for a wafer on the uppermost waferholding device to provide the wafer with a similar plasma cleaningenvironment as other wafers held underneath.
 16. A method for cleaning awafer, the method comprising: placing a wafer to be cleaned on awafer-holder; positioning the wafer-holder with the wafer thereon sothat the wafer-holder is held at an angle away from the vertical;applying a cleaning solution to the wafer held at the angle; anddraining the cleaning solution from the wafer, the wafer being held atthe angle facilitating the draining.
 17. A method for plasma cleaning awafer, the method comprising: placing a wafer to be plasma cleaned on awafer-holder; positioning a plurality of the wafer-holders with wafersthereon so that the wafers are held in a spaced stack; providing a coverabove the uppermost one of the wafers; and applying a cleaning plasma tothe wafers, the cover providing an exposure to the cleaning plasma tothe uppermost wafer that is similar to the wafers underneath theuppermost wafer.
 18. An optically transparent disk for bonding asemiconductor wafer thereto to provide support for the wafer, the diskhaving a diameter and formed from a chemical resistant material, whereinthe diameter of the disk is larger than the wafer's diameter byapproximately 3% or more.
 19. The disk of claim 18, wherein the diameterof the disk is larger than the wafer's diameter by approximately 5% ormore.
 20. The disk of claim 19, wherein the diameter of the disk islarger than the wafer's diameter by approximately 6% or more.
 21. Thedisk of claim 20, wherein the diameter of the disk is larger than thewafer's diameter by approximately 10% or more.
 22. The disk of claim 18,wherein the material includes sapphire.
 23. The disk of claim 18,wherein the material includes borosilicate.